Most operators today sit at the intersection of the data center cooling Venn diagram – traditional open-air cooling on one side, full liquid cooling on the other.. While room-level air conditioning is a simple and cost-effective approach for low-density environments, typically below 15kW per rack, its ability to scale is limited as rack densities inevitably rise.
The inherent mixing of hot and cold air drives up energy use and costs, as data center spaces are often overcooled to protect the hottest racks. Over time, this approach can lead to hot spots and temperature fluctuations, putting expensive equipment at risk.. On the other side of the spectrum, direct-to-chip and immersion liquid cooling provide highly effective means of managing heat generated by GPUs and CPUs, removing heat efficiently at the rack level in AI and high-performance computing environments.
Supporting densities of 50-250kW per rack and beyond, these technologies are designed for the next generation of compute.. However, they also require careful design, integration, and leak management – not to mention significant capital investment and operational complexity – that many operators are simply not prepared to take on in a single step..
When rack densities fall between 20-40kW, operators enter the “transition zone” – a critical range that demands a practical, risk-averse solution capable of bridging the gap between air and liquid cooling. The goal is to maximize the value of existing air cooling infrastructure while creating a stable foundation for future liquid cooling deployments.. – Getty Images.
Containment is still essential in modern cooling design. As operators navigate the transitional space between air and liquid cooling, containment emerges as a foundational technology across both air and liquid cooling environments.. Whether a facility relies entirely on air cooling or is beginning to deploy liquid cooling for high-density workloads, effective airflow management remains fundamental.
Even in data centers where heat is increasingly removed directly from CPUs and GPUs, a significant portion of the thermal load still depends on air cooling. That makes containment a practical middle-ground solution.. “The heat load rejected on a single chip has increased pretty severely over the past five years, so we’re seeing much higher heat loads within cabinet environments.
Because of that, there is an even more crucial need for proper airflow management and containment of that heat load,” says Saman Berookhim, senior product manager for cabinets and containment at Legrand.. Keeping cold supply air and hot exhaust air from mixing, containment has addressed the challenges of traditional air-cooled data centers for years.
Using simple, low-disruption physical barriers such as doors, panels, and overhead or end-of-row structures, containment creates predictable airflow paths through the data hall. The result is more consistent airflow temperatures, improved cooling efficiency, and greater control over thermal performance..
Air is more than capable of overcoming the last 10-15 percent in some of these higher-density environments. With hot and cold orientations, it’s free energy at that point Saman Berookhim, Legrand. Hot and cold aisle containment help maximize the performance of existing cooling infrastructure.
Cold aisle containment, typically involving a roof placed over a row of cabinets with in-row coolers, keeps cold air at the level of the IT equipment instead of allowing it to escape into the broader room. Hot aisle containment, meanwhile, functions more like a chimney, exhausting hot air vertically into the ceiling return plenum.
That plenum is connected to a cooling unit – a CRAC or CRAH unit located at the side of the room – where the air is conditioned before being returned to the data hall.. One of the most persistent misconceptions in the industry is that liquid cooling will address all heat management challenges.
In reality, even when direct-to-chip cooling is deployed, a meaningful portion of thermal load depends on effective airflow management and air cooling.. “For example, if you have direct-to-chip cooling on a particular chip, the rest of the components – like the RAM, other CPUs, and some other cores – will still get hot.
Air is more than capable of overcoming the last 10-15 percent in some of these higher-density environments without much added cost or infrastructure requirements. With hot and cold orientations, it’s free energy at that point,” Berookhim explains.. “Liquid cooling is a big factor in these higher-density environments, but it’s not the only factor,” he adds.
“It’s not about moving from one to another – it’s about how these two distinct capabilities for cooling can be implemented to achieve near-perfect cooling strategies for data centers.”. Optimizing what’s already in place. – Getty Images. Before operators jump straight to liquid, it is worth considering whether they have fully optimized the cooling infrastructure already in place..
“It’s really the basis for how you’re going to achieve the best cooling strategy for your data center. I like to use the analogy of cooling your home in the summertime while leaving the windows open.. “You would close those windows before turning the air conditioning up to its highest setting to achieve the coolest environment possible.
That’s what traditional airflow containment achieves in a data center,” says Berookhim.. The benefits are not limited to thermal performance either. There is a significant energy efficiency advantage attached to airflow optimization and containment – and a financial one as well..
Containment has long delivered a compelling return on investment through lower cooling energy consumption, and that value proposition becomes even stronger as AI-era heat loads rise, as Berookhim emphasizes:. “With the rising rack densities and AI workloads that we’re seeing across the board – from hyperscale operators to enterprise environments – data centers will naturally move along a cooling maturity curve from no containment, to aisle containment, to rear door heat exchangers, and eventually to liquid cooling.”.
Data centers will naturally move along a cooling maturity curve from no containment, to aisle containment, to rear door heat exchangers, and eventually to liquid cooling Saman Berookhim, Legrand. In that sense, containment is not simply a precursor to more advanced cooling; it is a financially justifiable investment in its own right..
To illustrate the impact, Berookhim points to a colocation provider facing utility power constraints and rising cooling costs. After implementing cold aisle containment with Legrand, the operator reduced energy consumption to the point that its utility provider issued a credit – demonstrating how airflow optimization can directly translate into measurable financial and capacity gains..
The model was subsequently replicated across other facilities facing similar challenges, lowering cooling operating costs while freeing up power capacity for revenue-generating IT equipment and improving overall PUE.. “Had they thought of containment as an integration option as pods and cages were being built, it would’ve been a lot simpler in their journey to cooling efficiency than when their power was essentially running out.
It wouldn’t have led to that roadblock,” he says.. The lesson learned here is not to skip the fundamentals. Liquid cooling will play an increasingly important role in high-density environments, but it shouldn’t come at the expense of foundational airflow management..
The rise of hybrid cooling strategies. For most operators, cooling modernization is an incremental journey, requiring a phased approach balancing performance requirements, operational risk, and existing infrastructure investments. Berookhim offers a word of advice:.
“Take a step back and understand what those heat loads really look like in the environment before implementing liquid cooling to begin with. Even when liquid cooling is fully implemented, it doesn’t deliver 100 percent cooling efficiency because other components generate heat and don’t receive the same cooling effect.”. – Getty Images.
This reality is driving greater interest in hybrid cooling architectures, particularly within the transition zone, where operators must balance performance, risk, and existing infrastructure. One increasingly popular option is the rear door heat exchanger (RDHx).. Mounted directly to the rear of a server rack, the RDHx captures heat from exhaust air as it leaves the servers and removes it through a liquid-based heat exchanger before it enters the room..
By extracting heat at the rack level, RDHx systems significantly reduce the burden on room-level cooling infrastructure while mitigating many of the airflow challenges associated with higher-density deployments. Because they can be retrofitted into existing facilities or be deployed in new builds, they offer a scalable path toward high-density computing without requiring disruptive infrastructure overhauls..
“A RDHx is a good mid-range density fill – you can get comfortably around 100kW, depending on your inlet and outlet water temperatures. They are a good transition strategy, as not all data centers are going to be operating at the highest power that we’re seeing in the market today, but they can also support the higher densities that are occurring,” Berookhim affirms..
For operators in the transition zone, RDHx offers a strategic bridge to expand the cooling capacity of existing white space, enabling higher rack densities and allowing facilities to support growing AI and HPX workloads without immediately committing to a complete liquid-cooled deployment.. In these environments, technologies such as containment, airflow optimization controls, and RDHx are increasingly being deployed alongside liquid cooling – not replaced by it..
Preparing facilities for future liquid cooling adoption. As AI workloads drive rack densities higher, the role of containment becomes even more important as the foundation of a phased cooling strategy that can evolve from air cooling to hybrid architectures, and, ultimately, liquid cooling..
Containment is your stepping stone to liquid technologies. Integrate that in your journey to higher heat load capacities Saman Berookhim, Legrand. For operators planning that journey, preparation matters.
Working with experienced partners and cooling-agnostic infrastructure solutions can help ensure today’s investments support tomorrow’s requirements, enabling facilities to scale as thermal demands increase.. “Containment is your stepping stone to liquid technologies, as there is still a risk that other heat sources can affect your environment without containment in mind.
Integrate that in your journey to higher heat load capacities,” Berookhim suggests.. As operators journey along the cooling maturity curve, the most effective strategies will not replace air with liquid; they will integrate both. Containment remains the proven, foundational technology that delivers immediate efficiency gains while creating a clear pathway to the next generation of high-density infrastructure..
To learn more about the benefits of aisle containment, visit Legrand.. More from Legrand. 09 Apr 2026.
24 Mar 2026. 31 Mar 2025
